LIX issues Area Forecast Discussion (AFD) at Sep 11, 5:51 AM CDT ...New AVIATION...618
FXUS64 KLIX 111051
AFDLIX
Area Forecast Discussion
National Weather Service New Orleans LA
551 AM CDT Fri Sep 11 2026
...New AVIATION...
.KEY MESSAGES...
Updated at 545 AM CDT Fri Sep 11 2026
- Deep tropical moisture moving into the area is causing localized
heavy rainfall and flooding across urban parts of the I-10/12
corridor.
- This elevated risk for localized heavy rainfall leading to
street flooding and overflowing of poor drainage will continue
on Friday and into Saturday.
&&
.SHORT TERM...
(Now through Monday)
Issued at 119 AM CDT Fri Sep 11 2026
Rinse and repeat is the name of the game for today and tomorrow as
a slow moving upper level trough axis slides through the Lower
Mississippi Valley and Gulf South. A plume of deep tropical
moisture will remain over the area through the period with PWATS
running between the 90th percentile and daily max for mid-
September both days. As temperatures warm into the mid to upper
80s, enough instability, as noted by SBCAPE of over 1000 J/KG,
will be in place to support convective updraft development.
Multiple rounds of shower and thunderstorm activity will develop
in the vicinity of a weakening low centered over coastal Louisiana
and then spread inland through the afternoon hours. Rainfall rates
of 2 to 3 inches per hour will be common and storm motion will be
5 to 10 mph each day. The end result will be continued potential
for localized flooding rainfall events to occur if storms become
anchored and backbuild on weak mesoscale boundaries like the
lakebreeze or seabreeze. If this occurs, these localized spots
could easily see 3 to 5 inches of rainfall fall in short period of
time. More urbanized areas with poor drainage or that are low
lying will have the greatest impacts in the form of street
flooding from these heavy rainfall events. Overall, the flooding
will remain isolated and the region remains in a level 1 out of 5,
marginal, risk of flash flooding today and tomorrow.
The upper level trough axis will shift to the east as we move into
Sunday and Monday and a broad upper level high will start to shift
toward the region from the west. As this high becomes more
centered over the area, increasing negative vorticity advection
and subsidence in the mid and upper levels of the atmosphere will
lead to both drying and warming aloft. PWATS will fall to between
the 75th and 90th percentile on Sunday and then further drop to
between the median and 75th percentile by Monday. The lack of deep
layer forcing aloft and weaker mid-level lapse rates will also
help to inhibit convective development a bit. Any convection will
tend to fire up more in the afternoon hours as temperatures climb
into the lower 90s and the convective temperature is reached. The
convection will also be more confined to pre-existing meso-scale
boundaries like the seabreeze or remnant outflow boundaries
resulting in more scattered coverage for both Sunday and Monday.
Overall, a return to a more typical late Summer weather regime is
expected as we move into the new week.
&&
.LONG TERM...
(Monday night through Thursday)
Issued at 119 AM CDT Fri Sep 11 2026
By Monday night, upper level ridging is expected to be centered over
Tennessee, and is forecast to stay in the same general area through
next Thursday. Surface high pressure over the Appalachians will
extend southwestward into the area. Forecast soundings indicate that
moisture should be sufficient for at least isolated to scattered
afternoon convection each day. If there's a day where most areas
would be dry (and hot), it'd probably be Tuesday.
This will bring us back to the summer pattern of afternoon
temperatures in the low to mid 90s and 30-50% PoPs in the
afternoons. These highs temps are about 5 degrees above normal for
the end of summer and combined with the humidity will put heat index
values in the 105-110 range, especially Tuesday, so advisories can't
entirely be ruled out.
&&
.AVIATION...
(12Z TAFS)
Issued at 545 AM CDT Fri Sep 11 2026
Saturated soils and a weak surface based inversion associated with
a rain cooled airmass from earlier in the night has allowed low
stratus and fog to develop at several of the terminals over the
past few hours. LIFR fog and stratus are impacting BTR, HDC, MCB,
and ASD with MVFR conditions noted at HUM and NEW. These
conditions will linger through 13-14z before quickly lifting as
temperatures warm and boundary layer mixing increases. There have
been some passing showers at GPT over the past few hours. These
showers are forming on the east side of a weak low over southeast
Louisiana and will continue to form for the next few hours. PROB30
wording is in place through 15z to reflect the passing convection.
The remainder of the terminals will see a mix of MVFR and VFR
conditions as a cumulus field ranging between 2000 and 3500 feet
forms. Additional rounds of showers and thunderstorms will then
develop over the area and impact all of the terminals between 17z
and 00z with periods of lightning, gusty winds, and reduced
visibilities. After 00z, convection will quickly wane with the
loss of daytime heating and prevailing VFR conditions will take
hold.
&&
.MARINE...
Issued at 119 AM CDT Fri Sep 11 2026
A weak area of low pressure will dissipate over the area today
with light and variable winds of 10 knots or less expected.
Tomorrow, winds will turn more south-southwesterly at 10 to 15
knots as a broad surface high over Florida becomes more dominant.
These conditions will persist into Saturday. The high will become
more centered over the eastern Gulf and southeastern United States
as we move into next week, and this will cause winds to turn more
south- southeasterly at 5 to 10 knots from Sunday onward. Seas
will generally remain in the 1 to 3 feet range with the highest
seas well offshore. Additionally, thunderstorm activity will
develop each day, peaking in the early to mid-morning hours, and
these storms will produce higher wind gusts, waterspouts, and
lightning concerns.
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&
$$
SHORT TERM...PG
LONG TERM....RW
AVIATION...PG
MARINE...PG
Source:
LIX issues Area Forecast Discussion (AFD) at Sep 11, 5:51 AM CDT ...New AVIATION...---------------
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